It is frequently necessary to utilize an existing folding system, using folding cylinders with varying numbers of sheets to be folded, in dependence on specific printing jobs. The German Patent Disclosure Document DE 38 38 314, Michalik, discloses a folding jaw and folding blade cylinder combination, which has an arrangement to adjust the spacing of the folding jaws, to thereby accommodate different numbers of sheets to be folded. The folding jaw cylinder has a cylinder shaft with a carrier arrangement formed of two carrier disks. The carrier disks support a movable folding jaw row; two further carrier disks carry fixed folding jaw rows. The carrier disks are suitably journalled in side plates or side frames of the folding apparatus. The carrier disks can be pivoted about the cylinder shaft by interposed slide bearings. They can be secured to the cylinder shaft by clutches. The cylinder shaft has an axial bore extending about one-third df its length, and a radial bore emanating therefrom. The two bores receive positioning shafts and an associated positioning spindle which are coupled by suitable bevel gears with a drive wheel of the folding jaw cylinder and with adjustment carriers, located in the carrier or support disks. A drive gear is driven by a positioning motor. The positioning motor receives positioning commands in the form of electrical signals, supplied thereto by a three-step controller. The three-step controller is coupled to a command input which permits introduction of input values representative of paper thickness, and further to a feedback sensor which measures the thickness of a paper web or paper web assembly.
It has been found that the arrangement has difficulties in operation since the positioning drive is remote from the positioned element, namely the folding jaws. In order to transfer positioning movement, a plurality of transmission elements must be used, such as gear belts, sprockets in engagement therewith, spindles, bevel gears and the like. The control must be accurate and reflect the input signals, so that all these transmission elements must be accurately constructed with as little play as possible. An additional difficulty arises due to the bore in the drive shaft, which is subjected to high loading. The drive shaft of the folding jaw cylinder is mechanically weakened by this bore, which impairs its long-time stability.